On 31 Dec 2020 02:14:44 GMT, A. Dumas 
declaimed the following:

>Martin Gregorie  wrote:
>> It answers the first part of his problem: getting signals to and from a
>> user process to a D-9 or D-25 serial port without having to build
>> something on a GPIO expansion card.
>
>He. Never. Mentioned. D9, D25 or RS232. Stop living in 1975.

 Most of the hardware I've had to interface with has required RS-232
levels. In truth, the only serial port device I have that did not need
RS-232 levels is a Kenwood R-5000 receiver -- and in its day a 5V TTL to
RS-232 level shifter was a separate accessory or something one had to build
in order to control it. Kenwood finally put real RS-232 ports on the
TS-570/590/2000 rigs.





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 Wulfraed                 Dennis Lee Bieber         AF6VN
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